Lecture 4: Separating

Question 1

What does separating entail in mechanical processes? (5 factors)

Answer 1

Removing material without changing its structure.
Objective: avoid heating up the material and altering its crystalline structure.
Minimize damage to the material.
Goal: lose as little material as possible.
Aim to avoid creating chips or sawdust.

Question 2

What are the different techniques used in mechanical separating without chip-forming?

Answer 2

Cutting (like a knife).
Punching – removing
the inner part
Nibbling

Question 3

What are the techniques used in mechanical separating with chip-forming?

Answer 3

Sawing.
Grinding, friction sawing.
Milling

Question 4

What are 5 methods involved in physical separating?

Answer 4

Flame-cutting, plasma-cutting, laser-cutting.
Wire electro discharge machining (wire-EDM).
Waterjet-cutting.

Question 5

Punching -

Answer 5

Removing the inner part

Question 6

Blanking-

Answer 6

Removing the outer part

Question 7

Perforating -

Answer 7

making holes on the inside of
the product.

Question 8

Notching-

Answer 8

Make notches(holes on the outside)

Question 9

in Lancing-

Answer 9

The material is sliced or cut without producing a slug or separating the workpiece

Question 10

Slitting -

Answer 10

Making an indentation in the product.

Question 11

What is the principle behind mechanical separating without chip-forming?

Answer 11

involves removing a section of the sheet with a punch that lowers.
happens when the sheet has insufficient space to deform.
leads to rough materials and sharp edges

Question 12

What 3 characteristics are involved in parting during mechanical separating?

Answer 12

1.Uses a universal tool with a bottom blade and a die.
2.Clamp prevents tilting.
3.Moving blade cuts material under a shear angle, reducing forces.

Question 13

What 3 characteristics occurs in slitting during mechanical separating?

Answer 13

Die and a punch, same as in parting
Uses rotating cutters.
Follows a specific geometry to give a precise separation line.

Question 14

What is the process of punching in mechanical separating?(2)

Answer 14

1.Involves perforating the sheet with a punch.
2.Hole shape determined by the shape of the tool.

Question 15

What are the factors influencing punching force?

Answer 15

• Forces in punching
  o Linear with sheet thickness
  o Linear with shear strength
  o Linear with perimeter of the tool geometry – equals the outer line of the punched shape (a.k.a
  the circumference of parameter of the tool geometry) ➔ that determines the punching force:

Question 16

Rule of thumb:

Answer 16

Never make holes that are smaller or even close to
the sheet thickness

Question 17

What is a progressive die in mechanical separating?

Answer 17

A complex die with multiple punches.
Allows for punching and forming multiple holes in one strip of material.

Question 18

punching force =

Answer 18

(sheet thickness) x (shear strength of material) x (circumference of parameter
of the tool geometry)

Question 19

Nibbling includes

Answer 19

multiple steps to reach the final shape for we want (approximating the shapes we want)
Achieves the final shape through successive punches.

Question 20

What is sawing in mechanical separating?

Answer 20

Involves cutting material with a straight-line saw.
Generates a small amount of sawdust during the process.
the bigger the radio, the higher the cutting speed.

Question 21

What is grinding in mechanical separating?

Answer 21

Utilizes small teeth to grind away material.
Requires cooling to prevent excessive temperature rise during operation.

Question 22

What are two facors of physical separating in manufacturing?

Answer 22

1.Utilizes high-energy methods like flame-cutting, plasma-cutting, laser-cutting, wire electro discharge machining (EDM), or waterjet-cutting.
2.Focuses on energy to separate materials rather than using mechanical force.

Question 23

What distinguishes physical separating from mechanical separating?

Answer 23

Non-mechanical process.
Independent of mechanical properties of materials.This means:
- Possibility of a narrow cut.
- Heat effected zone.

Question 24

5 characteristics that describe flame cutting in physical separating

Answer 24

1.Sets fire to the material, burning it away.
2.Rapid burning with potential damage to the cut edge.
2.Easy contour cutting but not ideal for thin sheets, but cutting very thick materials is possible
4.The burned surface will not be shiny ➔ high roughness
5.Multi-layer cutting is possible

Question 25

advantages/disadvantage

Answer 25

+The big advantage of flame cutting is that you can bring the tools for cutting wherever you want, there is not special machinery needed.
- The disadvantage of flame cutting is that it is not a subtle process.

Question 26

source of energy used in flame cutting (oxyacetylene cutting)

Answer 26

i. Burning mix of gasses
ii. Combustion temperature < melting temperature - the temperature at which the material starts burning if
we add oxygen is lower than the melting temperature
iii. Oxidation is a source of energy/heat to maintain the process ➔ might cause rust

Question 27

Explain plasma cutting in physical separating.

Answer 27

Uses extreme temperatures generated by ionized gas.
Faster and more precise than flame cutting and better surface finish.
Requires a larger power supply and machine.

Question 28

Discuss laser cutting in physical separating.

Answer 28

Utilizes concentrated light energy for cutting.
We can reach very narrow cuts ➔ small heat
affected zone
Can cut steel up to 30mm thickness
Even more precise finish than flame cutting and plasma cutting

Question 29

we can cut with:

Answer 29

We can cut with oxygen ➔ oxidation, more
energy ➔ we can burn harder and thicker layers of
sheet
i. This process decreases the quality and will
introduces rust

Question 30

why do we need a pulsed beam in laser cutting

Answer 30

Cutting sharp corners – if we use regular laser beam, we will burn
the material ➔ we need a pulsed beam (which is not continuous)
➔ it does not overheat the material

Question 31

Whatever you do in laser cutting any cut parts will have

Answer 31

a typical X shape that will not be cut
away ➔ you will never have parallel cuts ➔ the thicker the material, the bigger the X shape

Question 32

Explain in 3 wire electro discharge machining (Wire-EDM) in physical separating.

Answer 32

Uses high current and voltage difference to erode material.
Precise but slow process with smooth surface finish.
Electrode wire continuously replaced due to erosion.

Question 33

Geometry of EDM cutting

Answer 33

• defined by how we move the wire
  i. Accurate and smooth surface finish
  ii. Subtle process

Question 34

Waterjet cutting –

Answer 34

Uses high-pressure water stream to cut materials.
Abrasive particles added for cutting hard materials.
Can cause oxidation due to use of water and oxygen.
a. High pressure - ~400 Mpa (can cut paper without wetting it)
b. Can cut textile, plastics
d. Not a very subtle process